1. Field of the Invention
The present invention pertains generally to devices, assemblies and systems for backflow prevention, and more particularly to a compact, light weight, low maintenance double check valve backflow prevention apparatus of modular construction.
2. Description of the Background Art
Backflow prevention devices are widely used to prevent undesirable flow reversal under low flow, static or backpressure situations wherein clean upstream fluid sources can be contaminated by downstream fluid. Backflow prevention devices typically comprise one or two check valves, housed within a valve body, which undergo closure under backflow, backpressure or back siphonage conditions. The use of backflow prevention devices is generally required by law for cross-connected water supplies where potable water could undergo contamination due to flow reversal or back pressure conditions.
An important drawback in currently used back flow preventer devices is the difficulty associated with accessing the internal check valves for maintenance and repair. Convention backflow prevention devices typically use a bulky, heavy cast housing with a side port tube or extension and a separately cast port cover. The check valves are typically bolted to seats or fixtures within the housing, and can only be reached through the side port tube, which hinders access to the check valves. Maintenance and replacement of the check valves requires a person to reach through the side port tube and loosen bolts, compression rods or other internal hardware in order to remove the check valves, and thus tends to be a difficult and expensive operation. This type of cast housing additionally is expensive to manufacture and requires a substantial amount of space to accommodate the side port tube and cover.
Accordingly, there is a need for a backflow prevention apparatus which is compact and light weight, which is easy and inexpensive to manufacture, which does not have a side port tube, and which provides easy access to internal check valves. The present invention satisfies these needs, as well as others, and generally overcomes the deficiencies found in the background art.
The invention is a backflow prevention apparatus of light weight, modular construction which provides quick and easy access to internal check valves. In its most general terms, the invention comprises a tubular valve body having a lateral opening, at least one check valve positioned within the flow stream of the tubular valve body, a movable sleeve which fits over the valve body and is configured to cover the lateral opening in the valve body, and seal means, associated with the sleeve and valve body, for providing a fluid tight seal between the sleeve and valve body.
By way of example, and not of limitation, the tubular valve body has openings at first and second ends, and the lateral opening is flangeless. Preferably, the backflow preventer comprises a first, upstream check valve and a second, downstream check valve each having thereon a stop or ridge thereon. The check valves may be clapper-type check valves, poppet check valves, or any other conventional fluid check valve. The upstream check valve fits within the lateral opening and is positioned adjacent an upstream edge thereof, with the stop on the upstream check valve fitting against or abutting the upstream edge of the lateral opening. The downstream check valve fits within the lateral opening and is positioned adjacent the downstream edge thereof, with the stop on the downstream check valve fitting against or abutting the downstream edge of the lateral opening. Preferably, one or more spacers or compression rods are positioned between the upstream and downstream check valves to hold the check valves in position.
In the preferred embodiments, the sleeve is structured and configured to fit over the tubular valve body, and is slidably movable with respect to the valve body such that the sleeve can move between a first position in which the sleeve covers the lateral opening, and a second position in which the sleeve is moved away from the lateral opening and the lateral opening is exposed. The sleeve may include external annular flanges to facilitate manipulation of the sleeve on the valve body. In other embodiments, the sleeve may be longitudinally split so that two halves of the sleeve fit over the valve body and come together in a xe2x80x9cclamshellxe2x80x9d arrangement.
Preferably, a vent element with a threaded portion is used to secure the sleeve to an internal spacer positioned between the check valves when the sleeve is positioned to cover the lateral opening. The sleeve may alternatively be secured in position by means of on or more bolts or fasteners which secure the sleeve to the tubular valve body or to a spacer element positioned under the sleeve.
The seal means associated with the sleeve preferably comprises first and second annular seals which extend around the inner surface of the sleeve and sealingly engage the valve body. Preferably, one annular seal is positioned adjacent an upstream edge of the sleeve, and the other annular seal is positioned adjacent a downstream edge of the sleeve, so that when the sleeve is positioned over the lateral opening, the sleeve and annular seals define a fluid tight cover for the lateral opening. The seals means may alternatively comprise annular seals located on the outer surface of the valve body which sealingly engage the sleeve when the sleeve is positioned over the lateral opening.
In order to access the check valves in the valve body, the vent element is unthreaded and the sleeve is slidably moved to expose the lateral opening in the valve housing. The spacer holding the check valves in place is removed, and the check valves are removed from the valve housing via the lateral opening. Since the lateral opening does not have a side extension or flange, the check valves are easy to reach, and no further disassembly is required for detaching and removing the check valves. The apparatus is easily re-assembled by replacing the check valves in position against the upstream and downstream edges of the lateral opening, placing the spacer between the check valves, and sliding or moving the sleeve back into position over the lateral opening.
An object of the invention is to provide a backflow prevention apparatus which is compact and light weight.
Another object of the invention is to provide a backflow prevention apparatus which is easy and inexpensive to manufacture.
Another object of the invention is to provide a backflow prevention apparatus of modular construction.
Another object of the invention is to provide a backflow prevention apparatus which does not have a side port tube.
Another object of the invention is to provide a backflow prevention apparatus which does not require a formed port cover.
Another object of the invention is to provide a backflow prevention apparatus which allows quick and easy access to check valves for service, repair and replacement.
Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing the preferred embodiment of the invention without placing limitations thereon.